This invention relates to antennas in general and particularly to an antenna that can be used in a miniature portable radio receiver, such as a pager receiver.
Conventional loop antennas for use at high UHF Frequencies such as 930 MHz in a miniature receiver are difficult to resonate and feed. When the loop area, or aperture, is made sufficiently large to obtain reasonable efficiency, the loop inductance is so large that an unreasonably small capacitor is required to resonate it.
One known UHF loop antenna useful in the 440 to 460 Mhz range comprises smaller loop aperture in parallel with a larger loop aperture; so that the aperture area is substantially determined by the larger loop aperture while the reactance is determined substantially by the smaller loop aperture. In that way a capacitive resonating and feeding network (using capacitors of realistic value) can be utilized. That design does not scale to the 930 MHz band conveniently since the mechanical arrangement is complicated and the antenna becomes too cumbersome for simple and automated assembly.
Another known antenna is fed by a shunt transmission line. In that antenna, feeding and matching are accomplished by extending the center conductor of a coaxial line along a portion of a loop circumference. Such a feed and match is simple and effective if it is mechanically stable.